Stem thinning in potato as a pre-selection index

Using the potato seedling B7906-1, stem thinning was carried out on plants having three, four, or five stems per hill. Treatments ranged from intact plants to those thinned by one, two, or three stems each. Data on the effect of stem thinning on yield and other vegetative parameters were analysed using an analysis of variance. Unlike leaf parameters, stem height and number of stolons per plant generally decreased with an increase in stem thinning. Within a control group, represented by the intact plants having the three stem densities used for treatments, the degree of association among different vegetative parameters and the measure of their contribution towards yield were determined by correlation and path coefficient analyses, respectively. Given the effect of number on weight of tubers per plant, the assessment of yield as affected by stem density treatments was confined to the former parameter. Among all parameters, number of stolons per plant was the most effective contributor to number of tubers harvested. The decrease in that parameter as a result of stem thinning, however, was not accompanied by a corresponding decrease in tuber number. The following relationship could be discerned: as number of stolons per plant decreased several stem parameters increased. Based on correlation and path analyses, it is suggested that the induced increase in number of compound leaves per stem could have compensated, directly or indirectly, for the adverse effect of stolon number on yield. Through stem density manipulation, the yield output of a variety in response to quantitatively induced, more diverse, vegetative characteristics could be evaluated.